Traditionally, individual skates, dollies, castors or rollers have been used to support heavy equipment or machinery for movement thereof from one area to another. A roller is inserted under each corner of a machine, for example, in order to provide rolling support to facilitate the moving of the machine. Typically, the rollers raise the machine 4–6″ off the ground, and the only connection provided between the machine and the rollers is the weight of the machine bearing down on the rollers. However, if the floor over which the machine is being moved is uneven, and should one of the rollers encounter a rut or protrusion in or on the surface, it is quite easy for one of the rollers to become dislodged from the load and for that corner of the machine to fall to the ground. When considering top-heavy machines, such a drop could result in the entire machine tipping over with disastrous results.
Various other mobile supports have been developed that include some type of frame that connects four corner rollers together in order to avoid the situation of having one of the corner rollers becoming dislodged from beneath the load. However, the structures are not easily adaptable to different sized loads since the frames consist of rigid members that are specifically fabricated to provide a certain low degree of adjustability, and they are usually cumbersome to adjust. Furthermore, the load is often raised a number of inches off the ground which still presents a hazard if the load were to become dislodged from one corner of the support.
Canadian Patent No. 2,323,848 to Hewitt discloses a mobile base assembly for supporting and moving machinery. The base assembly comprises corner members having platforms that support the load, extension members connecting the corner members together, support wheels and castor wheels, and at least two stops for supporting the base in a stationary position. The corner and extension members utilize a series of holes that are aligned with respect to each other, and then secured together using nuts and bolts. This allows the size of the base to be adjusted to accommodate a variety of load sizes. Although the base is adjustable, the use of nuts and bolts to join the corner and extension members together is cumbersome. Furthermore, the base is not easily adapted to accommodate extra support wheels or castors, which limits the load carrying capacity of the mobile base.
U.S. Pat. No. 5,044,645 to Eltvik teaches a U-shaped dolly apparatus for supporting and moving heavy objects. The device surrounds the intended load on three sides, with the weight of the load being supported by the two end members while the side member telescopes to adjust to the length of the load. The end members include large wheels, however the wheels do not pivot or swivel to allow for easy steering of the apparatus. Once again, adjustability is provided by means of specifically fabricated pieces that are aligned and locked together.
U.S. Pat. No. 5,358,264 to Hewitt reveals an I-shaped apparatus for supporting and moving heavy objects, typically machinery. The device essentially comprises two parallel end members connected by a centrally located longitudinal member creating the I-shape. One of the end members mounts a pair of pivoting castors, arranged at opposite ends thereof, while the other end member has a single centrally positioned swivelable wheel. The apparatus is of a fixed size and accordingly cannot be adjusted to fit different-sized loads.
U.S. Pat. No. 4,066,272 to Cobb discloses dolly means comprising individual units that have a frame with a supporting surface for engaging the heavy load, and four independent axles mounted beneath the surface with wheels rotatably mounted thereon. Each axle is capable of vertical movement, which allows one or both of its wheels to move up or down to respond to an uneven surface. The use of the dolly means, however, will often require more than one of the individual units with, for example, one of the units being placed under each corner of the load. Cobb's device improves upon the conventional use of skates or rollers by introducing independent axles beneath a single platform, which helps to reduce the likelihood of the device slipping out from beneath the load since the units can adjust to uneven surfaces. However, the possibility of one of the units becoming dislodged still exists as there is nothing holding each unit together in an overall assembly.